Features of the Largest Earthquake Seismic Cycles in the Western Part of the Aleutian Subduction Zone

Leopold I Lobkovsky,Dmitry A Alekseev,Yurii V Gabsatarov,Irina S Vladimirova

doi:10.3390/geosciences12030107

Abstract

We discussed the peculiarities of the seismic cycle in Aleutian subduction zone, characterized by an oblique subduction setting. It was shown that the orientation of the plate convergence vector relative to the subduction zone axis can have a significant impact on the preparation and occurrence of the largest earthquakes in subduction zones. In particular, from the analysis of the seismic activity occurring in the western part of the Aleutian island arc, it was found that the seismic cycles here are shorter than in the eastern part of the arc. It was revealed that the strongest earthquakes, repeating in the same areas of the western part of the Aleutian subduction zone, differ both in magnitude and length of the fault zone. Taking into account the oblique subduction setting, we proposed the keyboard model of the largest megathrust earthquakes generation as a mechanism potentially capable of explaining the reduction in the seismic cycle duration and noticeable differences in the spatial extent and localization of the fault zones of events with similar magnitudes occurring in the same segment of the western half of the Aleutian subduction zone.

Highlights

Studying seismic process features is of great importance for solving urgent problems of geodynamics and geophysics, large-magnitude earthquake forecasting
Based on retrospective analysis of the spatio-temporal distribution of the fault zones associated with the largest earthquakes in the Aleutian subduction zone, we revealed a distinctive feature of the seismic process in the western part of the Aleutian subduction zone, which is the seismic cycle shortening, compared to the eastern part of the island arc
Our analysis showed that the orientation of the plate convergence vector relative to subduction zone axis can have a significant impact on the generation of the megathrust earthquakes in subduction zones

Summary

Introduction

Studying seismic process features is of great importance for solving urgent problems of geodynamics and geophysics, large-magnitude earthquake forecasting. Establishing parameters of seismic cycles associated with megathrust earthquakes will significantly improve seismic hazard assessment and provide new data for solving the fundamental problem of earthquake prediction. The average recurrence periods of the large-magnitude earthquakes are on the order of 100–1000 years at active plate boundaries and 1000–10,000 years in their stable inner regions [1]. Since seismic activity is controlled by nearly stationary processes, such as plates’ motion, the seismic regime, in particular the seismogenic zone, is expected to display stationary behavior. The occurrence of a largemagnitude earthquake itself has a direct impact on the stress-strain state of the neighboring regions of the seismogenic zone, thereby shortening or prolonging the duration of the seismic cycle

Objectives

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Discussion

Conclusion